What IgG class or subclass should I use for my primary antibody?

The nature of your sample will determine which IgG class or subclass primary antibody is most appropriate.

The main factor to consider is the species the primary antibody is raised in must be different from the species of your sample. Another factor to consider is whether to choose a monoclonal or polyclonal primary antibody. Both have their own pros and cons. Monoclonal primary antibodies have very high homogeneity and recognize only a single epitope on the antigen. They generate less background noise and are less likely to cross-react with other proteins. However, their high specificity prevents them from working in a full range of species. Polyclonal primary antibodies recognize multiple epitopes on any antigen, are more tolerant to minor changes to the antigen, and work well to amplify the signal from low expression proteins. However, they can produce a high background signal and are more prone to variability between batches.